1. Field of the Invention
The invention relates to electronic surveillance (ES) and electronic counter measure (ECM) systems and, in particular, to a portable device capable of inserting previously collected and stored or fabricated digitized radio frequency (RF) pulsed data into an electronic surveillance system to realistically simulate the complex and dense RF environment of a particular theater of operation or threat scenario. The invention further relates to the method by which the device creates and inserts said data.
2. Description of the Background
Electronic Surveillance (“ES”) systems are used on modern United States (U.S.) Navy ships. These systems receive RF signatures in the form of pulse data and digitize them. The data is then processed in order to identify signals and determine the nature of the signals, threatening or non-threatening, for the purpose of threat awareness and self-defense. The data processing is typically accomplished by sending the data through a pulse processor, filtering it, and comparing the filtered data to stored sets of parameters. Monitoring the performance of processors within ES systems currently in use on U.S. Navy ships is required for continued improvement in recognition capabilities.
Up until now, such monitoring was accomplished by analyzing recordings of the ES system's response to known external stimuli. The external stimuli is supplied by radiating RF modulated pulses at the ES system antennas, injecting RF modulated pulses into the ES system cables, or using system specific built-in-test (BIT) capabilities. Each of these methods supply RF modulated pulses that the ES system has to process into digital pulse descriptor words (PDWs). However, due to the ever-increasing complexity and density of emissions in the RF spectrum, this method of assessing ES system performance is out-dated and insufficient. Both injecting RF and built-in-test (BIT) do not provide the total RF environment. Radiating at the antennas on a ship will capture the RF environment, reflections, etc but is often costly and time consuming. Adequate assessment of the performance capabilities of an ES system requires an in-depth analysis of the system's response in light of all of the RF pulse activity for a given time period. Only with such an assessment can there be a realistic improvement in the development of radar and threat recognition algorithms.
Many ES systems and electronic counter measure (ECM) systems have the ability to sample and temporarily store the RF parameter data of a singular received RF pulse. This pulse is finely sampled across its duration. This sampling of information allows the re-creation of the pulse for output. However, modern ES and ECM systems do not possess long-term multi-pulse storage capability. In ECM systems the goal of the memory is to affect a short delay in the retransmission of data. This delay equates to range when viewed from a hostile perspective. Digital radio frequency memory (DRFM) or other memory is used to capture, store and then retransmit RF energy a short time later. This is often referred to as an RF delay line. Once the data has been re-transmitted, it is no longer held in memory. For example, U.S. Pat. Nos. 4,891,646, 4,713,662 and 4,743,905 to Wiegand, U.S. Pat. No. 4,885,587 to Wiegand, et. al., and U.S. Pat. No. 4,928,104 to Schaffer all discuss various forms of DRFM for use within ECM systems. Specifically, these DRFMs are designed for use within active radar jamming systems. In each form the purpose of the DRFM is to allow the radar jamming system to capture received radar signals, manipulate or alter them in time or phase, as necessary, and return them on demand to confuse enemy radar systems. U.S. Pat. No. 5,032,839 to Even-Or employs optical RF memory for the same purpose.
Several other prior art references also disclose the use of short-term memory to improve the speed and accuracy of ECM or ES systems.
U.S. Pat. No. 4,145,691 to Freeling et al. patents a memory system which finds particular use in ECM systems. It uses memory to establish a feedback loop to re-circulate RF burst signals which are emitted by enemy radar systems.
U.S. Pat. No. 4,217,580 to Lowenschuss discloses a complete ECM system. In this system RF signals are converted to digital words. The digital words are then pre-sorted. Once a predetermined number of digital words associated with one radio frequency signal is collected, that data is passed to a computer. This computer will then compare the signature to that of a library, recognize the threat and determine the counter technique called jamming. U.S. Pat. No. 4,879,561 to Inkol discloses a filter system for analyzing interleaved PDWs received from a multiplicity of radar signals. This system incorporates a buffer memory. The buffer memory is organized to allow data corresponding to a particular radar emitter to be efficiently accessed for further analysis within the radar system.
U.S. Pat. No. 4,025,920 to Reitboeck et al. discloses an apparatus and method for identifying incoming radar signals by comparing them with stored sets of parameters. Similarly, a radio frequency detection and collection system (RFD/CS) produced by Wide Band Systems, Inc. uses an antenna array and instantaneous frequency measurement (IFM) receivers to collect RF signals and convert them into PDWs. The PDWs are then transmitted to a computer workstation for analysis. The purpose of the computer workstation in this RFD/CS system is to compare the incoming PDWs with stored parameters in order to identify the intercepted emissions.
Parent application Ser. No. 10/774,643 filed on Feb. 6, 2004, for “Descriptor Word Collector”; inventors: Slutzky, Barry; Kluender, Andrew, describes a portable PDW Collector for passively capturing and storing (as extractor files) all digitized RF pulse data received by an ES system receiver prior to filtering by the ES system pulse processor. The PDW Collector is comprised of a personal computer and an electronics unit, called a PDW Extractor. This PDW Collector is designed for easy and unobtrusive integration with an ES system. It is also easily removable to a laboratory environment for play back of the received data and analysis of the system's response thereto. The PDW Collector does not, however, allow collected extractor files to be inserted back into an ES system.
A simulator called VariGen™ has recently been introduced by Varilog Research, Inc. This simulator system employs Windows™ based software which allows the user to describe complex emitter parametric agility and allows the user to approve the emitter description. Hardware units then create and insert simulated pulsed and constant wave (CW) RF signals into an electronic warfare (EW) system, such as the AN/SLQ-32(V). However, this simulator is incapable of inserting into the ES system actual recorded PDW data that captures all the nuances of a ship, including own-ship reflections, sea reflections, roll and pitch effects, and electromagnetic interference (EMI).
None of the above-mentioned references discloses a system that is capable of inserting previously recorded or fabricated RF pulse data into an ES system to realistically simulate a complete RF pulse environment.
Thus, there is a need for a portable PDW Generator (generator) designed to insert previously recorded or fabricated digitized RF pulse data into an ES system. This portable generator will allow for an accurate and realistic simulation of a total RF pulse environment present in a given threat scenario. For example, a PDW Collector captures and records an actual threat situation (i.e. missile attack against a naval vessel) and stores the data as extractor files. The extractor files are then are uploaded to a generator, converted to generator files and inserted into the ES system of the same ship or another ship in another part of the world to realistically simulate the particular event. Such a generator would provide a realistic, convenient and cost-effective portable simulation device and testing tool that can be easily integrated into an ES system. Additionally, such a system is needed for use as a trouble-shooting tool. For example, ships that are having problems with their ES system will be able to use the PDW Collector to capture and record a problem and then use the generator to systems analysts to trouble-shoot the problem by controlled insertion back into the ES system.